1. Field of the Invention
The present invention relates to an LED driving circuit, and more particularly to a double-output high-efficiency LED light-modulating circuit having twin-bus framework.
2. Description of the Prior Art
Light-emitting diode (LED) is one of the conventional lighting devices; comparing to the traditional incandescent bulb, LED lamp shows the advantages of high luminous efficiency and energy-saving. Because the LED device cannot be directly electrically connected to the AC outlet on the wall, LED driving circuits are developed and proposed. Currently, the LED driving circuits are divided into linear driving circuit and switch driving circuit, wherein the switch driving circuit often includes a power factor correction circuit.
Please refer to FIG. 1, which illustrates a framework diagram of a conventional switch LED driving circuit. As shown in FIG. 1, the conventional switch LED driving circuit 1′ consists of a rectifying unit 11′, a power factor correcting unit 12′, a DC/DC converting unit 13′, an output unit 14, a PFC controlling unit 15′, and a convertor controlling unit 16′. In the switch LED driving circuit 1′, the power factor correcting unit 12′ is first-stage circuit, such as boost converter or buck converter, and the DC/DC converting unit 13′ is second-stage circuit for modulating the output voltage.
The aforesaid switch LED driving circuit 1′ performs high power-correction effect and is capable of modulating the output voltage rapidly. However, as shown in FIG. 1, the power factor correcting unit 12′ and the DC/DC converting unit 13′ are controlled by the PFC controlling unit 15′ and the convertor controlling unit 16′, respectively, and the two controlling units not only cause the whole circuit of the switch LED driving circuit 1′ become complex, but also result in that the whole circuit area of the switch LED driving circuit 1′ cannot be effective reduced. Moreover, the power dissipation of the two controlling units also cause a low power conversion efficiency to the switch LED driving circuit 1′.
Thus, in view of the conventional switch LED driving circuit still has shortcomings and drawbacks, the inventor of the present application has made great efforts to make inventive research thereon and eventually provided a double-output high-efficiency LED light-modulating circuit.